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2003 chevy trailblazer_ls
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522 Posts
Discussion Starter #1
It seems like my little TB has the flu! Alot of strange symptoms lately. Other than the security light coming on and off by itself and the 4x4 selector light either not on or blinking then going off. (sometimes they stay on an work fine) but wth the recent snow in chicago I went and put it in 4x4 hi drove some...came to a intersection to turn at...start to fishtail..and think 4x4 hi seems different than last year!!

Further investigation revealed 4x4hi not working as well as a4x4. Placed in N and tried 4x4lo. put it into drive and it worked. switched back and still only 2wd.

I have read the threads about the fuse #8 and will try that when I can get to the fuse box. Could this be a TCCM issue? Does the PCM have any effect or link to the 4x4? Could it just be the selector switch? One last question..what noise should I be hearing while he 4x4 should be engaging? When I use to switch last year I could hear a slight hum for about a sec or 2. When I try it now I dont hear anything except 4x4lo and its a much louder hum and then a clunk if that makes sence:undecided
 

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2003 chevy trailblazer_lt
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it could be the switch it self.. i would start there... i think its 20 bucks with shipping cant remember... but as u said...

Alot of strange symptoms lately.
i would check out that ignition switch first... whether or not this 4 wheel drive problem is caused by that.. i dont know... but past that i would try a new switch first (try the cheapest solution first) it fixed mine.. even tho mine is still a bit skitzo and works when it wants.. but that is where i would start... that doesnt solve it... it can be 2 other things... either the encoder motor or the TCCM... some have been solved by getting the TCCM reflashed.. others had to get a whole new unit...


on a side not... can u hear the encoder motor and the spline disconnect make a whirl noise to let u know it changed?
 

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2003 chevy trailblazer_ls
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Discussion Starter #3
it could be the switch it self.. i would start there... i think its 20 bucks with shipping cant remember... but as u said...



i would check out that ignition switch first... whether or not this 4 wheel drive problem is caused by that.. i dont know... but past that i would try a new switch first (try the cheapest solution first) it fixed mine.. even tho mine is still a bit skitzo and works when it wants.. but that is where i would start... that doesnt solve it... it can be 2 other things... either the encoder motor or the TCCM... some have been solved by getting the TCCM reflashed.. others had to get a whole new unit...


on a side not... can u hear the encoder motor and the spline disconnect make a whirl noise to let u know it changed?
I got the ignition switch on the way. Thanks for the help. I read on another thread that a member put it in 4x4hi manualy, but did not say how. Has anyone heard of this and how is it done?
 

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2003 chevy trailblazer_lt
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I got the ignition switch on the way. Thanks for the help. I read on another thread that a member put it in 4x4hi manualy, but did not say how. Has anyone heard of this and how is it done?
i dont know bout that... i was under the belief that it was all sealed inside the TC... not accessible from the outside..

do this... this will help figure it out...

This can be done with the engine off but in Assc on... make sure its somewhat quiet around..
start in 2Hi, flip it to A4WD and listen if u can hear a little whirl sound.. if u do then the front spline disconnect is moving...
then flip for A4WD to 4Hi and listen again for another whirl. should come from rite under ur seat.. that would be the transfer case...

if we know that.. mite be able to help ya better and or eliminate something...
 

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2003 chevy trailblazer_ls
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Discussion Starter #5
i dont know bout that... i was under the belief that it was all sealed inside the TC... not accessible from the outside..

do this... this will help figure it out...

This can be done with the engine off but in Assc on... make sure its somewhat quiet around..
start in 2Hi, flip it to A4WD and listen if u can hear a little whirl sound.. if u do then the front spline disconnect is moving...
then flip for A4WD to 4Hi and listen again for another whirl. should come from rite under ur seat.. that would be the transfer case...

if we know that.. mite be able to help ya better and or eliminate something...
Thanks, Ill give it a try
 

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2004 gmc
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...dont hear anything except 4x4lo and its a much louder hum and then a clunk if that makes sence:undecided
It does. The transfer case motor, as hatchet-man says, is a lower pitched sound. Find another working trailvoy, and use the trick of putting it in neutral with the ignition on and running the switch through the modes. The front axle actuator is a very high pitched whine that only operates from 2WD to A4WD and vice versa. The encoder motor on the side of the transfer case moves a little bit for each of the three possible transitions. (2WD to A4WD, A4WD to 4HI, and 4HI to 4LO.)

The transfer case is sealed, but there's a shaft out the side that the encoder motor turns to change its modes. If I got stuck in 2WD on a trail that NEEDED 4WD to get out of, I'd remove the encoder motor and turn that shaft with a vise grip. All it takes is 20-30 degrees to change modes. I'd post scans from the shop manual if needed, but this would only be an emergency thing to do. For a pavement-driven trailvoy, I can only imagine doing it to get back into 2WD if the encoder motor or TCCM failed while it was in 4HI or 4LO modes.

When you said 4LO mode worked, are you sure the front axle engaged by feeling the scrubbing on pavement in turns? Or could it have just gone into the 2.7-to-1 reduction ratio, but still driving only the rear wheels?
 

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2003 chevy trailblazer_ls
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Discussion Starter #7
It does. The transfer case motor, as hatchet-man says, is a lower pitched sound. Find another working trailvoy, and use the trick of putting it in neutral with the ignition on and running the switch through the modes. The front axle actuator is a very high pitched whine that only operates from 2WD to A4WD and vice versa. The encoder motor on the side of the transfer case moves a little bit for each of the three possible transitions. (2WD to A4WD, A4WD to 4HI, and 4HI to 4LO.)

The transfer case is sealed, but there's a shaft out the side that the encoder motor turns to change its modes. If I got stuck in 2WD on a trail that NEEDED 4WD to get out of, I'd remove the encoder motor and turn that shaft with a vise grip. All it takes is 20-30 degrees to change modes. I'd post scans from the shop manual if needed, but this would only be an emergency thing to do. For a pavement-driven trailvoy, I can only imagine doing it to get back into 2WD if the encoder motor or TCCM failed while it was in 4HI or 4LO modes.

When you said 4LO mode worked, are you sure the front axle engaged by feeling the scrubbing on pavement in turns? Or could it have just gone into the 2.7-to-1 reduction ratio, but still driving only the rear wheels?
It seemed to handle better in Lo, but then again I did not drive it far. Now this morning I was going to pull into my garage and check the fuse. Since there was a good amout of snow on my drive way the back wheels just spun in 2wd and awd and 4hi, when I put it in lo, It seemed to engage, however it had a wierd kind of pulsating when I took my foot off the brake at idle. Since I was unsure what would happen if I gave it gas (i didnt want to slide sideways and hit the nannys car) I just put it back in 2wd and went on with the day.
 
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